Stats & Research Design

Front 1

INTERNAL VALIDITY

Back 1

Allows an investigator to determine if there is a causal relationship between independent and dependent variables.

Front 2

Threats to Internal Validity (8)

Back 2

1. Maturation
2. History
3. Testing
4. Instrumentation
5. Statistical Regression
6. Selection
7. Attrition (Mortality)
8. Interactions with selection

Front 3

Maturation

Back 3

**Threat to Internal Validity**
Any biological or psychological change that occurs within subjects during course of study as function of time, is not relevant to the research hypotheses, and affects the status of most subjects on the dependent variable in a systematic way.

Front 4

Examples of Maturation

Back 4

Fatigue, boredom, hunger, physical and intellectual growth.

Front 5

History

Back 5

**Threat to Internal Validity**
Threatens a study's internal validity when an external event systematically affects the status of subjects on the dependent variable.

Front 6

How is History controlled

Back 6

by including more than one group in the study and randomly assigning subjects to groups.

Front 7

Testing

Back 7

**Threat to Internal Validity**
Taking a test can alter a person's performance on the test when it is readministered. Testing can threaten internal validity whenever exposure to a test might alter the subjects performance on subsequent tests.

Front 8

Instrumentation

Back 8

**Threat to Internal Validity**
Changes in accuracy or sensitivity of measuring devices or procedures during the study can confound the study results.

Front 9

Statistical Regression

Back 9

**Threat to Internal Validity**
Tendency of extreme scores on a measure to "regress" toward the mean when the measure is readministered to the same group.

Front 10

Selection

Back 10

**Threat to Internal Validity**
Whenever the method used to assign subjects to treatment groups results in systematic differences between groups at the beginning of the study.

Front 11

Attrition (mortality)

Back 11

**Threat to Internal Validity**
Poses a threat to internal validity when subjects who drop out of one group differ in an important way from subjects who drop out of another group.

Front 12

Interactions with selection

Back 12

**Threat to Internal Validity**
When groups are initially nonequivalent, selection can act alone or can interact with other factors to threaten a study's internal validity.

Front 13

Name the Threats to External Validity (4)

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1. Interaction between testing and treatment
2. Interaction between selection and treatment
3. Reactivity
4. Multiple Treatment Interference

Front 14

Interaction between testing and treatment

Back 14

**Threat to External Validity**
The administration of a pretest can "sensitize" subjects to the purpose of research study and alter their reaction to the independent variable.

Front 15

Name two ways to control for Interaction between testing and treatment

Back 15

1. Not administering a pre-test
2. Solomon four-group design (enables investigator to measure the impact of pretesting on both internal and external validity of study).

Front 16

Interaction between selection and treatment

Back 16

**Threat to External Validity**
Subjects included in research study can have characteristics that make them respond to the independent variable in a particular way. When this occurs, the results of the study cannot be generalized to people who don't have those characteristics. (i.e. When subjects are volunteers, they tend to be more motivated than non-volunteers and consequently more responsive to the IV).

Front 17

Reactivity

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**Threat to External Validity**
Research participants can respond to the independent variable in a particular way because they know their behavior is being observed.

Front 18

Demand Characteristics (Included in category of Reactivity)

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Cues in the experimental setting that inform subjects of the purpose of the study or suggest what behaviors are expected of them.

Front 19

Multiple Treatment Interference (Order effects, Carryover effects)

Back 19

**Threat to External Validity**
When a study involves exposing each subject to two or more levels of the IV (within-subjects design) the effects of one level of the independent variable can be affected by previous exposure to another level. When this occurs, the results of the study cannot be generalized to situations in which people are only exposed to one level of the independent variable.

Front 20

How can Multiple Treatment Interference be controlled?

Back 20

Counterbalanced design (i.e. Latin Square)

Front 21

What is a Counterbalanced Design

Back 21

Used to control multiple treatment interference, when different subjects receive the levels of the independent variable in a different order.

Front 22

A study's ___ validity is limited by its ___ validity, but a high degree of ___ validity does not guarantee ___ validity

Back 22

A study's external validity is limited by its internal validity, but a high degree of internal validity does not guarantee external validity